Among the α-heterosubstituted cyclopropylmetals α-selenocyclopropyllithiums represent some of the most valuable synthetic intermediates. They are quantitatively prepared from selenoacetals of cyclopropanones and butyllithiums, are thermally stable at ∼−78° for several hours and are particularly nucleophilic especially towards carbonyl compounds. The cyclopropyl derivatives containing a selenenyl moiety have been transformed to selenium free derivatives such as alkylidene cyclopropanes, vinyl cyclopropanes, allylidene cyclopropanes, cyclobutanones and α-silyl cyclopropyllithiums. The latter compounds have been used as starting material for the synthesis of alkylidene cyclopropanes and cyclopentenyl derivatives. α-Seleno cyclobutyllithiums, which are available in two steps from cyclobutanones, also permit the synthesis of various selenium free homologues such as alkylidene cyclobutanes, vinyl cyclobutanes, oxaspirohexanes and cyclopentanones.

Synthesis and synthetic applications of 1-metallo-1-selenocyclopropanes and -cyclobutanes and related 1-metallo-1-silylcyclopropanes

Complex eliminations proceed with rearrangements. They’occur in most of the different branches of preparative organic chemistry. By relative notations of positions, they are ordered and named in a classifying way, independent from the respective reaction mechanism. Structural peculiarities of particular types are also included and distinguished. If only one or two groups or bonds migrate, the classifications are distinct and unequivocal. Nevertheless, in case of two migrating residues it is occasionally necessary to evaluate by labelling, which type the reaction belongs to. In the case of multiple migrations, it is necessary to divide the reaction into partial steps via (several) postulated or proved intermediates. The presented material shows synthetical potential and points out that most types can be realized according to different reaction mechanisms and under most different reaction conditions.

Complex Eliminations; Eliminations with Rearrangements

Silicon-controlled rearrangement versus krief-reich reaction in β-seleno-γ-silyl alcohols : A new stereoselective synthesis of terminally-substituted allylsilanes

Regio- and stereoselective synthesis of allyltrimethylsilanes via krief-reich elimination in β-seleno-γ- silyl alcohols

Trans 1,2-functionalization of cycloalkenes using selenium intermediates

2-Hydroxy-3-trimethylsilyl-propyl selenides, readily prepared by the reaction of α-phenylselenoaldehydes and trimethylsilylmethyl-lithium, are transformed into primary allylic selenides and β-trimethylsilylpropanals by acid-catalysed dehydroxysilylation accompanied by a phenylseleno-shift, and by silver-induced rearrangement of the trimethylsilylmethyl group, respectively.

Akiko Yamamoto

Papers

New rearrangement of phenylseleno- and trimethylsilylmethyl groups in 2-hydroxy-3-trimethylsilylpropyl selenides